Last winter while I was laid off from work I went to work building solar heaters for all my south facing windows. I got the idea fromBYCers who posted a link to coloradowindpower.com and I thought why not give it a try. Rather than attach the glass to the front of the heater I built it so that the unit nests directly against the window pane. I also modified the design to place the fan farther from the frame to insure better air flow through the entire heater and I shortened the design so as to only cover the lower pane. The entire unit, sloar electric panel $30.00 (from harbor freight) the fan, $15.00 (from radio shack) the frame $15.00 and about forty aluminum cans ( we have a $0.10 deposit) $4.00. A one time investment that should easily pay for itself in one or two years and continue to produce heat for years to come. Assuming the sun shines! In the summer I just remove the entire unit from the window. This is the heater from inside the house The planter (chives) keeps the solar panel powering the fan flush to the upper windowpane. Air inlet at the bottom (so I am heating the indoor air rather than the outdoor air) and fan at the top. This is another view from outside. It is difficult to see the painted cans but the unit works beautifully. I put a similar unit in every south facing window in the house. The last cloudless day with full sun and an outside temperature of 20 degrees F. I held a thermometer in front of the fan and the air temperature coming from the unit was 104 degrees. Combined these heaters will raise the temperature in the living room, dining room and kitchen about 6 degrees and the furnace will not kick on from ten in the morning till 6 at night.